The present invention relates to a heat-developable image-recording material used for, in particular, photomechanical processes. More precisely, the present invention relates to a heat-developable image-recording material for scanners or image setters, particularly, a heat-developable image-recording material suitable for color photomechanical processes, which is free from wrinkles and excellent in dimensional stability upon heat development.
As one of the light exposure methods of photographic light-sensitive materials, there has been known a method for image formation of so-called scanner type, wherein an original is scanned, and a silver halide photographic material is light-exposed based on the obtained image signals to form a negative or positive image corresponding to the image on the original.
In the case where an image output from a scanner on a film is further printed directly on a printing plate without a reversal step, or a scanner light source having a soft beam profile, a light-sensitive material for scanners exhibiting ultra-high contrast property has been desired.
A large number of light-sensitive materials comprising a support having thereon a light-sensitive layer are known, where the image formation is performed by imagewise exposing of the light-sensitive material. Of these, a technique of forming an image by heat development is a system capable of satisfying the issue of environmental protection or simplifying the image formation means.
In recent years, reduction of the amount of waste processing solutions is keenly demanded in the field of photomechanical processes from the standpoint of environmental protection and space savings. To cope with this, techniques are required to produce light-sensitive heat-developable materials for use in photomechanical processes, which can be effectively exposed by a laser scanner or laser image setter and can form a clear black image having high resolution and sharpness. Such light-sensitive heat-developable materials can provide to users a simple heat development processing system which is dispensable uses solution-type processing chemicals, and does not destroy the environment.
Methods for forming an image by heat development are described, for example, in U.S. Pat. Nos. 3,152,904 and 3,457,075 and D. Morgan and B. Shely, Imaging Processes and Materials, xe2x80x9cThermally Processed Silver Systemsxe2x80x9d A, 8th ed., page 2, compiled by Sturge, V. Walworth and A. Shepp, Neblette (1969). The light-sensitive material used contains a light-insensitive silver source (e.g., organic silver salt) capable of reduction, a photocatalyst (e.g., silver halide) in a catalytic activity amount, and a reducing agent for silver, which are usually dispersed in an organic binder matrix. This light-sensitive material is stable at room temperature. However, when it is heated at a high temperature (e.g., 80xc2x0 C. or higher) after the exposure, silver is produced through an oxidation-reduction reaction between the silver source (which functions as an oxidizing agent) capable of reduction and the reducing agent. The oxidation-reduction reaction is accelerated by the catalytic action of a latent image generated upon exposure. The silver produced by the reaction of the silver salt capable of reduction in the exposure region provides a black image and this presents a contrast to the non-exposure region. Thus, an image is formed.
Although heat-developable light-sensitive materials of this type have hitherto been known, most of those light-sensitive materials utilize a polyester film as a support produced by stretching, and hence suffer from a drawback that images are deformed upon heat development due to thermal dimensional change (mainly thermal shrinkage) of the support.
Further, a binder contained in the image-forming layer also simultaneously causes dehydration shrinkage and thermal expansion upon heat development, and these phenomena produce wrinkles of the film because they are different from thermal behavior of the support. Thus, only films unsuitable for color printing, wherein the films are laminated for use, are eventually produced.
As techniques for preventing such dimensional change and wrinkles arisen from the heat development, there have been proposed various thermal treatments for relaxing internal distortion produced during the film production by stretching. For example, JP-A-3-24936 (the code xe2x80x9cJP-Axe2x80x9d as used herein means an xe2x80x9cunexamined published Japanese patent applicationxe2x80x9d), JP-A-64-64833, JP-A-8-211547, JP-A-3-97523, JP-A-61-154829, JP-A-3-97523, JP-A-57-109946 and the like can be mentioned.
In fact, the methods disclosed in those documents can alleviate the degree of thermal shrinkage of supports produced as films by biaxial stretching. However, they cannot reduce the dimensional change over time after the heat development.
A color photomechanical process is carried out by using four films for the four colors, i.e., Y, M, C and K. When these four films are simultaneously subjected to light exposure and heat development, any particular problem is not caused. However, the light exposure and the heat development are often performed on different occasions for these four films. In such a case, because the time after the heat development is different for each film, the sizes of the films may not fit each other, which often causes color deviation.
Therefore, there has been desired a technique capable of providing a heat-developable light-sensitive material exhibiting excellent dimensional stability irrespective of handling conditions.
Accordingly, an object of the present invention is to provide a heat-developable image-recording material that shows small dimensional change over time after the heat development and small dimensional change before and after the heat development, and is free from generation of wrinkles during the heat treatment. Another object of the present invention is to provide a heat-developable image-recording material affording images of excellent photographic properties.
The aforementioned objects have been achieved by the present invention, which provides a heat-developable image-recording material which is heat-developed at a development temperature of from 80xc2x0 C. to 140xc2x0 C., and comprises, on both sides of a support, undercoat layers comprising a vinylidene chloride copolymer containing at least 70% by weight of vinylidene chloride monomer repeating units and having a thickness of 0.3 xcexcm or more for each.
In a preferred embodiment of the present invention, an image-forming layer containing an organic silver salt, reducing agent, and light-sensitive silver halide is provided on the support. On the image-forming layer, at least one protective layer is preferably provided. The vinylidene chloride copolymer preferably contains 70-99.9% by weight of the vinylidene chloride monomer repeating units and 0.1-5% by weight of carboxyl group-containing vinyl monomer repeating units. The vinylidene chloride copolymer preferably has a weight average molecular weight of 45000 or less. The support is preferably composed of biaxially stretched polyester. The heat-developable image-recording material of the present invention is preferably subjected to heat treatment at a temperature of 130xc2x0 C. to 185xc2x0 C. after the undercoat layers are coated on the support. The rate of heat dimensional change of the heat-treated support, when it is heated at 120xc2x0 C. for 30 seconds, is preferably xe2x88x920.03% to 0.01% for the machine direction (MD), and 0% to 0.04% for the transverse direction (TD). As binders for the image-forming layer and the protective layer, a polymer latex is preferably used.